Carbon Dioxide Based Auxiliary Cooling System

ABSTRACT

The present application provides a cascade refrigeration system. The cascade refrigeration system may include a first side cycle, a second side cycle with a second side cycle carbon dioxide refrigerant, and an auxiliary cooling system to cool the second side cycle carbon dioxide refrigerant in the event of a power outage. The auxiliary cooling system may include an auxiliary carbon dioxide refrigerant.

TECHNICAL FIELD

The present application and the resultant patent relate generally to refrigeration systems and more particularly relate to a carbon dioxide based auxiliary cooling system for a refrigeration system that may be free of the use of hydrofluorocarbons and the like.

BACKGROUND OF THE INVENTION

Cascade refrigeration systems generally include a first side cooling cycle, or a high side cycle, and a second side cooling cycle, or a low side cooling cycle. The two cooling cycles interface through a common heat exchanger, i.e., a cascade evaporator-condenser. The cascade refrigeration system may provide cooling at very low temperatures in a highly efficient manner.

Current refrigeration trends promote the use of carbon dioxide and other types of natural refrigerants as opposed to conventional hydrofluorocarbon based refrigerants. Unlike hydrofluorocarbons, however, carbon dioxide based systems may lose refrigerant during power outages. In the case of a power outage, the carbon dioxide based system may start gaining heat such that the refrigerant pressure may rise and exceed the design pressure of the overall refrigeration system. The refrigeration system generally must be vented to the atmosphere in such a situation.

In order to avoid venting the refrigerant, carbon dioxide based refrigeration systems may include a backup condensing unit with an independent power source to keep the carbon dioxide cool. These known backup devices, however, generally use hydrofluorocarbon based refrigerants such that the refrigeration system as a whole cannot be considered truly “green” or hydrofluorocarbon free.

There is thus a desire for a refrigeration system such as cascade refrigeration systems that provide auxiliary cooling without the use of hydrofluorocarbons. Such an auxiliary cooling system would provide efficient cooling in a truly hydrofluorocarbon free design.

SUMMARY OF THE INVENTION

The present application and the resultant patent thus provide a cascade refrigeration system. The cascade refrigeration system may include a first side cycle, a second side cycle with a second side cycle carbon dioxide refrigerant, and an auxiliary cooling system to cool the second side cycle carbon dioxide refrigerant in the event of a power outage. The auxiliary cooling system may include an auxiliary carbon dioxide refrigerant.

The present application and the resultant patent further provide a method of providing auxiliary cooling in a refrigeration system. The method may include the steps of flowing a natural refrigerant through a first side cycle, flowing a carbon dioxide refrigerant through a second side cycle, providing an auxiliary cooling system to cool the flow of the carbon dioxide refrigerant in the case of a power loss, and flowing an auxiliary carbon dioxide refrigerant through the auxiliary cooling system.

The present application and the resulting patent further provide a carbon dioxide based refrigeration system. The carbon dioxide based refrigeration system may include a receiver, a carbon dioxide refrigerant, and an auxiliary cooling system in communication with the receiver to cool the carbon dioxide refrigerant in the event of a power outage. The auxiliary cooling system may include an auxiliary carbon dioxide refrigerant.

These and other features and improvements of the present application and the resultant patent will become apparent to one of ordinary skill in the art upon review of the following detailed description when taken in conjunction with the several drawings and the appended claims.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic diagram of a known cascade refrigeration system with a high side cycle and a low side cycle.

FIG. 2 is a schematic diagram of a cascade refrigeration system with a carbon dioxide base auxiliary cooling system as may be described herein.

FIG. 3 is a schematic diagram of an alternative embodiment of a carbon dioxide based auxiliary cooling system as may be described herein.

DETAILED DESCRIPTION

Referring now to the drawings, in which like numerals refer to like elements throughout the several views, FIG. 1 shows an example of a cascade refrigeration system 100. The cascade refrigeration system 100 may be used to cool any type of enclosure for use in, for example, supermarkets, cold storage, and the like. The cascade refrigeration system 100 also may be applicable to heating, ventilation, and air conditioning and/or different types of industrial applications. The overall cascade refrigeration system 100 may have any suitable size or capacity.

Generally described, the cascade refrigeration system 100 may include a first or a high side cycle 110 and a second or a low side cycle 120. The high side cycle 110 may include a high side compressor 130, a high side oil separator 140, a high side condenser 150, a high side receiver 160, and a high side expansion device 170. The high side cycle 110 also may include a suction/liquid heat exchanger 180 and a suction accumulator 190. The high side cycle 110 may include a flow of a natural refrigerant 200. The natural refrigerant 200 may include a flow of ammonia, a flow of hydrocarbons, and the like. Other components and other configurations may be used herein.

The low side cycle 120 similarly may include a low side compressor 210, a low side oil separator 220, a low side receiver 230, a low side expansion device 240, and one or more low side evaporators 250. The low side cycle 120 may include a medium temperature loop 260 with a pump 270 and a number of flow valves 280 as well as a low temperature loop 290. An accumulator 300 also may be used therein. The low side cycle 120 may include a flow of a carbon dioxide based refrigerant 310 and the like. Other components and other configurations may be used herein.

The two cycles 110, 120 may interface through a cascade evaporator/condenser 320. The respective flows of the refrigerants 200, 310 may exchange heat via the cascade evaporator/condenser 320. The cascade evaporator/condenser 320 may have any suitable size or capacity. Other components and other configurations may be used herein.

The natural refrigerant 200 may be compressed by the high side compressor 210 and condensed in the high side condenser 150. The refrigerant 200 may be stored in the high side receiver 160 and may be withdrawn as needed to satisfy the load on the cascade evaporator/condenser 320. The refrigerant 200 then may pass through the high side expansion device 170 and returns to the high side compressor 130. The suction/liquid heat exchanger 180 may be used to sub-cool the refrigerant 200 before entry into the cascade evaporator/condenser 320.

The low side cycle 120 may be similar. The carbon dioxide based refrigerant 310 may be compressed by the low side compressor 210 and then pass through the cascade evaporator/condenser 320. The refrigerant 310 may be stored within the low side receiver 230 and withdrawn as needed. The refrigerant 310 may pass through one or more low side expansion devices 240 and one or more low side evaporators 250. The low side cycle 120 may be separated into the low temperature loop 290 and the medium temperature loop 260.

The cascade refrigeration system 100 also may include an auxiliary cooling system 330. The cooling auxiliary system 330 may be used to cool the flow of the carbon dioxide refrigerant 310 via an interface with the low side receiver 230 or elsewhere. The auxiliary cooling system 330 may include an auxiliary compressor 340, an auxiliary condenser 350, and an auxiliary expansion device. The cooling auxiliary system 330 may include a generator 370 or other type of independent power supply. The auxiliary cooling system 330 may interface with the low side cycle 120 via an auxiliary condenser/evaporator 380. Known auxiliary cooling systems 330 generally use a hydrofluorocarbon based refrigerant 390 such as R404A or R407A. Other components and other configurations may be used herein.

FIG. 2 shows a cascade refrigeration system 400 as may be described herein. The cascade refrigeration system 400 may include the same or a similar high side cycle 110 and low side cycle 120. The two cycles may interface via the cascade evaporator/condenser 320 and the like. As described above, the low side cycle 120 includes the flow of the carbon dioxide based refrigerant 310.

The cascade refrigeration system 400 also may include a carbon dioxide based auxiliary cooling system 410. The carbon dioxide auxiliary cooling system 410 may include an auxiliary compressor 420, an auxiliary condenser 430, and an auxiliary expansion device 440. The carbon dioxide auxiliary cooling system 410 may include an auxiliary generator 450 or other type of independent power supply. The carbon dioxide auxiliary cooling system 410 may interface with the low side cycle 120 via an auxiliary condenser/evaporator 460 or other type of heat exchange device. The carbon dioxide auxiliary cooling system 410 may include a flow of a carbon dioxide based refrigerant 470 therein. Other types of natural refrigerants also may be used herein. Other components and other configurations may be used herein.

In the event of the loss of power, the carbon dioxide auxiliary cooling system 410 may be used to cool the flow of the carbon dioxide refrigerant 310 in the low side cycle 120 via the carbon dioxide refrigerant 470 circulating therein and interfacing at the auxiliary condenser/evaporator 460. The cascade refrigeration system 400 thus is truly a hydrofluorocarbon free system. The carbon dioxide based auxiliary cooling system 410 may provide a faster overall response time in a proactive method of cooling the flow of carbon dioxide refrigerant 310 without venting. Multiple carbon dioxide auxiliary cooling systems 410 may be used herein.

FIG. 3 shows an alternative embodiment of a carbon dioxide auxiliary cooling system 500 as may be described herein. The carbon dioxide auxiliary cooling system 500 may include an auxiliary compressor 510, an auxiliary gas cooler 520 or condenser, and an auxiliary expansion device 530. The carbon dioxide auxiliary cooling system 500 also may include an auxiliary generator or other type of independent power source. The carbon dioxide auxiliary cooling system 500 also may include a flow of a carbon dioxide based refrigerant 540 therein. Other components and other configurations may be used herein.

The carbon dioxide auxiliary system 500 may tie directly into the low side cycle 120 via the low side cycle receiver 230 for heat exchange therewith. The carbon dioxide auxiliary system 500 thus avoids the need for an auxiliary condenser/evaporator and/or pump in a truly a hydrofluorocarbon free system. The carbon dioxide based auxiliary system 500 also may provide a faster overall response time in a proactive method of cooling the flow of carbon dioxide refrigerant 310 without venting.

Although the carbon dioxide based auxiliary cooling systems have been shown in the context of a cascade refrigeration system, the carbon dioxide based auxiliary cooling systems may be used in any type of carbon dioxide refrigeration system. Specifically, any type of carbon dioxide refrigeration system using a large receiver tank and the like.

It should be apparent that the foregoing relates only to certain embodiments of the present application and the resultant patent. Numerous changes and modifications may be made herein by one of ordinary skill in the art without departing from the general spirit and scope of the invention as defined by the following claims and the equivalents thereof. 

We claim:
 1. A cascade refrigeration system, comprising: a first side cycle; a second side cycle; the second side cycle comprising a second side cycle carbon dioxide refrigerant; and an auxiliary cooling system to cool the second side cycle carbon dioxide refrigerant in the event of a power outage; the auxiliary cooling system comprising an auxiliary carbon dioxide refrigerant.
 2. The cascade refrigeration system of claim 1, wherein the auxiliary cooling system comprises an auxiliary compressor and an auxiliary expansion valve.
 3. The cascade refrigeration system of claim 1, wherein the auxiliary cooling system comprises an auxiliary condenser.
 4. The cascade refrigeration system of claim 1, wherein the auxiliary cooling system comprises an auxiliary gas cooler.
 5. The cascade refrigeration system of claim 1, wherein the auxiliary cooling system comprises auxiliary condenser/evaporator.
 6. The cascade refrigeration system of claim 1, wherein the second side cycle comprises a second side cycle receiver and wherein the auxiliary cooling system is in communication with the second side cycle receiver.
 7. The cascade refrigeration system of claim 1, wherein the auxiliary cooling system comprises an auxiliary generator.
 8. The cascade refrigeration system of claim 1, wherein the first side cycle and the second side cycle interface via a cascade evaporator/condenser.
 9. The cascade refrigeration system of claim 1, wherein the first side cycle comprises a flow of an ammonia or a hydrocarbon refrigerant.
 10. The cascade refrigeration system of claim 1, wherein the first side comprises a suction/liquid heat exchanger.
 11. The cascade refrigeration system of claim 1, wherein the first side cycle comprises a first side compressor, a first side condenser, and a first side expansion device.
 12. The cascade refrigeration system of claim 1, wherein the second side cycle comprises a second side compressor, a second side expansion device, and a second side evaporator.
 13. The cascade refrigeration system of claim 1, wherein the second side cycle comprises a medium temperature loop and a medium temperature loop.
 14. The cascade refrigeration system of claim 1, further comprising a plurality of auxiliary cooling systems.
 15. An method of providing auxiliary cooling in a refrigeration system, comprising: flowing a natural refrigerant through a first side cycle; flowing a carbon dioxide refrigerant through a second side cycle; providing an auxiliary cooling system to cool the flow of the carbon dioxide refrigerant in the case of a power loss; and flowing an auxiliary carbon dioxide refrigerant through the auxiliary cooling system.
 16. A carbon dioxide based refrigeration system, comprising: a receiver; a carbon dioxide refrigerant; and an auxiliary cooling system in communication with the receiver to cool the carbon dioxide refrigerant in the event of a power outage; the auxiliary cooling system comprising an auxiliary carbon dioxide refrigerant.
 17. The carbon dioxide refrigeration system of claim 16, wherein the auxiliary cooling system comprises an auxiliary condenser.
 18. The carbon dioxide refrigeration system of claim 16, wherein the auxiliary cooling system comprises an auxiliary gas cooler.
 19. The carbon dioxide refrigeration system of claim 16, wherein the auxiliary cooling system comprises an auxiliary generator.
 20. The carbon dioxide refrigeration system of claim 16, wherein the carbon dioxide refrigeration system comprises a cascade refrigeration system. 